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351.
Numerical Investigation of Boundary-Layer Evolution and Nocturnal Low-Level Jets: Local versus Non-Local PBL Schemes 总被引:3,自引:0,他引:3
Kesu Zhang Huiting Mao Kevin Civerolo Stephen Berman Jia-Yeong Ku S. Trivikrama Rao Bruce Doddridge C. Russell Philbrick Richard Clark 《Environmental Fluid Mechanics》2001,1(2):171-208
Numerical simulations of the evolution of the planetary boundary layer (PBL) and nocturnal low-level jets (LLJ) have been carried out using MM5 (version 3.3) with four-dimensional data assimilation (FDDA) for a high pollution episode in the northeastern United States during July 15–20, 1999. In this paper, we assess the impact of different parameterizations on the PBL evolution with two schemes: the Blackadar PBL, a hybrid local (stable regime) and non-local (convective regime) mixing scheme; and the Gayno–Seaman PBL, a turbulent kinetic energy (TKE)-based eddy diffusion scheme. No FDDA was applied within the PBL to evaluate the ability of the two schemes to reproduce the PBL structure and its temporal variation. The restriction of the application of FDDA to the atmosphere above the PBL or the lowest 8 model levels, whichever is higher, has significantly improved the predicted strength and timing of the LLJ during the night. A systematic analysis of the PBL evolution has been performed for the primary meteorological fields (temperature, specific humidity, horizontal winds) and for the derived parameters such as the PBL height, virtual potential temperature, relative humidity, and cloud cover fraction. There are substantial differences between the PBL structures and evolutions simulated by these two different schemes. The model results were compared with independent observations (that were not used in FDDA) measured by aircraft, RASS and wind profiler, lidar, and tethered balloon platforms during the summer of 1999 as part of the NorthEast Oxidant and Particle Study (NE-OPS). The observations tend to support the non-local mixing mechanism better than the layer-to-layer eddy diffusion in the convective PBL. 相似文献
352.
Background, Aim and Scope
Metal ions generally share the ability/tendency of interacting with biological material by forming complexes, except possibly for the heavy alkali metals K, Rb and Cs. This is unrelated to the metals being either essential for sustaining life and its reproduction, apparently insignificant for biology, although perhaps undergoing bioconcentration or even being outright toxic, even at low admission levels. Yet, those different kinds of metal-biomass interactions should in some way depend on properties describing coordination chemistries of these very metals. Nevertheless, both ubiquitously essential metals and others sometimes used in biology should share these properties in numeric terms, since it can be anticipated that they will be distinguished from nonessential and/or toxic ones. These features noted above include bioconcentration, the involvement of metal ions such as Zn, Mg, Cu, Fe, etc. in biocatalysis as crucial components of metalloenzymes and the introduction of a certain set of essential metals common to (almost) all living beings (K, Mg, Mo, Mn, Fe, Cu and Zn), which occurred probably very early in biological evolution by ‘natural selection of the chemical elements’ (more exactly speaking, of the metallomes).Materials and Methods
The approach is semiempirical and consists of three consecutive steps: 1) derivation of a regression equation which links complex stability data of different complexes containing the same metal ion to electrochemical data pertinent to the (replaced) ligands, thus describing properties of metal ions in complexes, 2) a graphical representation of the properties-two typical numbers c and x for each metal ion-in some map across the c/x-space, which additionally contains information about biological functions of these metal ions, i.e. whether they are essential in general (e.g. Mg, Mn, Zn) or, for a few organisms of various kinds (e.g. Cd, V), not essential (e.g. rare earth element ions) or even generally highly toxic (Hg, U). It is hypothesized that, if coordination properties of metals control their biological ‘feasibility’ in some way, this should show up in the mappings (one each for mono and bidentate-bonding ligands). 3) eventually, the regression equation produced in step 1) is inverted to calculate complex stabilities pertinent to biological systems: 3a) complex stabilities are mapped for ligands delivered to soil (-water) by green plants (e.g. citrate, malate) and fungi and, compared to their unlike selectivities and demands of metal use (photosynthesis taking place or not), 3b) the evolution of the metallome during late chemical evolution is reconstructed.Results
These maps show some ‘window of essentiality’, a small, contrived range/area of c and x parameters in which essential metal ions gather almost exclusively. c and x thus control the possibility of a metal ion becoming essential by their influencing details of metal-substrate or (in cases of catalytic activities) metal-product interactions. Exceptions are not known to be involved in biocatalysis anyhow.Discussion
Effects of ligands secreted, e.g. from tree roots or agaric mycelia to the soil on the respective modes (selectivities) of metal bioconcentration can be calculated by the equation giving complex stability constants, with obvious ramifications for a thorough, systematic interpretation of biomonitoring data. Eventually, alterations of C, N and P-compounds during chemical evolution are investigated — which converted CH4 or CO2, N2 and other non-ligands to amino acids, etc., for example, with the latter behaving as efficient chelating ligands: Did they cause metal ions to accumulate in what was going to become biological matter and was there a selectivity, a positive bias in favour of nowessential metals (see above) in this process? Though there was no complete selectivity of this kind, neither a RNA world in which early ribozymes effected most of biocatalysis, nor a paleoatmosphere containing substantial amounts of CO could have paved the way to the present biochemistry and metallomes.Conclusions
This way of reasoning provides a causal account for abundance distributions described earlier in the Biological System of Elements (BSE; Markert 1994, Fränzle &; Markert 2000, 2002). There is a pronounced change from chemical evolution, where but few transformations depended on metal ion catalysis to biology.Recommendations and Perspectives
The application of this numerical approach can be used for modified, weighted evaluation of biomonitoring analytical data, likewise for the prediction of bioconcentration hazards due to a manifold of metal ions, including organometallic ones. This is relevant in ecotoxicology and biomonitoring. In combining apoproteins or peptides synthesized from scratch for purposes of catalysing certain transformations, the map and numerical approaches might prove useful for the selection of central ions which are even more efficient than the ‘natural’ ones, like for Co2+ in many Zn enzymes.353.
Alparslan E Aydöner C Tufekci V Tüfekci H 《Environmental monitoring and assessment》2007,135(1-3):391-398
Water quality at Omerli Dam, which is a vital potable water resource of Istanbul City, Turkey was assessed using the first four bands of Landsat 7-ETM satellite data, acquired in May 2001 and water quality parameters, such as chlorophyll-a, suspended solid matter, secchi disk and total phosphate measured at several measurement stations at Omerli Dam during satellite image acquisition time and archived at the Marine Pollution and Ecotoxicology laboratory of the Marmara Research Center, where this study was carried out. Establishing a relationship between this data, and the pixel reflectance values in the satellite image, chlorophyll-a, suspended solid matter, secchi disk and total phosphate maps were produced for the Omerli Dam. 相似文献
354.
Quality parameters from 17 sampling stations from Lake Koronia and 18 from Lake Volvi were determined during sampling period
of one year. Physicochemical parameters (pH, conductivity, DO) did not show remarkable differences neither between sampling
sites nor between sampling periods. Nutrient concentrations (nitrogen and phosphorus compounds) were higher in lake Koronia
than in Volvi showing relatively small temporal and spatial variations. As far as heavy metals in sediments, lake Koronia
is considerably more polluted than Volvi lake especially with the metals Fe, Mn, Zn, Pb and Cd. The mean total concentrations
of metals in lake Koronia decrease in the order Mn > Zn > Cr > Pb > Cu > Fe > Cd. The mean total concentrations of metals
in lake Volvi decrease in the order Mn > Zn > Cr > Cu > Pb > Fe $>$ Cd. 相似文献
355.
356.
2005年11月26日在江西九江、瑞昌间发生了5.7级地震,震中烈度达7度强。瑞昌地震后,开展了对鄱阳湖口地区重大工程设计地震动参数的校核研究,分析了瑞昌地震后区域地震背景变化和地震震后活动趋势,对发震构造进行了综合判定,划分出了瑞昌潜在震源区,并针对该地区某大型桥梁进行了地震危险性分析和设计地震动工程参数的校核计算。结果表明,瑞昌地震是近场区外的中强地震,对鄱阳湖口地区设计地震动工程参数影响很小。本文的工作为破坏性地震震后重大工程设计地震动参数的校核工作提供了范例。 相似文献
357.
358.
359.
Arkian F Salahinejad M Bidokhti AA Meshkatee A 《Environmental monitoring and assessment》2008,140(1-3):325-330
Measurement of gross α, gross β activities and cosmogenic beryllium-7 (7Be) concentrations were made both daily and weekly during the years 2001–2004 from samples of atmospheric aerosols filtered
from the air at Tehran Nuclear Research Center (35 41′ N) and Zahedan (28 29′ N). Weekly aerosol samples collected with the
high-volume air samplers on cellulose filters were used to determine the 7Be contents of samples, using a semiconductor gamma spectrometer. Airborne dust samples were collected daily on fiber glass
filters and used to determine the gross β and gross α activities with automatic beta analyzer and a ZnS(Ag) counter, respectively.
In this work, the concentration and meteorological data were used to determine models for gross α, gross β and 7Be. The air concentrations of gross β and gross α activities and 7Be concentrations displayed lognormal distributions during the study period. Both β and 7Be have maximum activity concentrations during warm mid-year months. 相似文献
360.
针对固定源废气监测过程中出现的关于监测仪器使用方面(包括传感器、内置泵及日常的校准),监测参数(包括动压、过量空气系数),采样位置不符合要求、烟道面积过大,运行负荷如何确定等常见问题进行了分析、探讨与总结,并提出了相应的改进方法和建议。 相似文献